The present invention relates to methods of treating a subterranean formation with one-step furan resin compositions.
Hydrocarbon wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid, which also functions as a carrier fluid, is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed. Typically, particulate solids, such as graded sand, are suspended in a portion of the fracturing fluid and then deposited in the fractures. These particulate solids (generally referred to as “proppant” or “proppant particulates”) are placed within the fractures and form proppant packs that serve to prevent the fractures from fully closing once the hydraulic pressure is removed. As used herein, the term “proppant pack” refers to a collection of proppant particulates within a fracture. The proppant pack contains interstitial spaces between individual proppant particulates that aid in forming conductive paths through which fluids may flow.
Often, hydraulic fracturing operations result in the creation of loose particles formed from the subterranean formation due to the creation of fractures. Moreover, some subterranean formations comprise loose particles notwithstanding any fracturing operation being performed, formations having naturally occurring loose particles may find them even more numerous after fracturing. Additionally, the proppant particulates placed within a fracture in a subterranean formation may become dislodged from a proppant pack and themselves become loose particles within the subterranean formation. These loose particles may make it difficult to recover fluids from the wellbore (i.e., oil and gas). The movement of the loose particles can create plugging of the proppant pack, thus requiring additional drawdown pressure to produce the well. As used herein, the term “drawdown pressure” refers to the differential pressure that drives fluids from within a wellbore to the surface.
One approach designed to prevent the movement of loose particles in a wellbore in a subterranean formation (or to “stabilize” or “consolidate”) is the use of gravel packing or frac-packing techniques. As used herein, the term “gravel packing” refers to a particulate control method in which a permeable screen is placed in a wellbore in a subterranean formation and the annulus between the screen and the formation surface is packed with specially sized gravel or proppant particulates. The gravel or proppant particulates are designed to stop or filter loose particles (e.g., formation fines or particulates) from being produced with the formation fluids. The accumulation of particulates in the annulus is known in the art as a “gravel pack.”
As used herein, the term “frac-packing” refers to a combined hydraulic fracturing and gravel packing treatment. In such frac-packing operations, a substantially particulate-free fluid is generally pumped through the annulus between a permeable screen and a wellbore in the subterranean formation and into perforations through a casing, or directly into the wellbore in the case of open hole completions, at a rate and pressure sufficient to create or enhance at least one fracture. Thereafter, a treatment fluid comprising particulates (e.g., gravel or proppant particulates) is pumped through the annulus between the permeable screen and the wellbore in the subterranean formation and into the perforations through a casing such that the particulates are placed within the at least one fracture, as well as in the annulus between the permeable screen and the wellbore in the subterranean formation, thus forming both a proppant pack in the fracture and a gravel pack in the annulus between the permeable screen and the wellbore.
In both gravel packing and frac-packing operations, loose particles may still escape the confines of the gravel pack and flow into the wellbore opening. This may be particularly true if the loose particles have a particularly variable size range with many small sized loose particles, such that the gravel pack is not capable of preventing the majority of loose particles from migrating through the pack.
Another technique for controlling the movement of loose particles in wellbores involves treating the formation (or proppant particulates) with a resin to facilitate consolidation of the loose particles within the formation and prevent them from migrating from the formation. However, consolidating agents are often difficult to handle, transport, and clean-up. For example, consolidating agents may cause damage to subterranean treatment equipment due to their inherent tendency to form a sticky or tacky surface. For this reason, furan resins, which do not pose the same handling problems because they are not internally catalyzed and which are cost-advantageous are often used. However, furan resins require an acid catalyst to help activate the polymerization of the resin in temperatures less than about 250° F. and typically require the addition of a corrosion inhibitor to protect iron and steel components in the wellbore from the acid. Corrosion inhibitors often lose their effectiveness at approximately 230° F. and must be carefully designed so as to function properly with the furan resin. Thus, while furan resins are beneficial in stabilizing loose particles in a wellbore in a subterranean formation, they are placed as a sequential fluid system and require specifically designed corrosion inhibitors that may not be operable at certain operational temperatures. Accordingly, an ongoing need exists for optimized furan resin treatments to stabilize loose particles in subterranean formations.